The present Application claims priority from Korean Patent Application No. 10-2002-0056348 filed in the Republic of Korea on Sep. 17, 2002, which Korean Application is incorporated in full by reference herein.
1. Field of the invention
The present invention relates to an image projecting apparatus, and more particularly, to an image projecting apparatus that realizes an image by using optical switches in a square matrix arrangement and optical switches in single file arrangement.
2. Description of the Related Art
A projector is an image projecting apparatus that displays an image by projecting an input image signal onto a screen. The image projecting apparatus is generally used in places such as presentation room, theater, and even a home.
Conventionally, a large screen image was realized by magnifying an image on a liquid crystal display (LCD) or a cathode ray tube (CRT) through a lens and then projecting it onto a screen. Although such an image may be enlarged, it is not provided at a high picture quality. In order to overcome this problem, an image projecting apparatus using a digital micromirror device (DMD) panel has been suggested.
The DMD is a semiconductor optical switch using a micromirror. The micromirror controls reflection of light in accordance with input of an image signal. Being digital, the DMD provides a high quality color representation and brightness. Furthermore, since there is no need for A/D or D/A conversion, a clearer image is obtainable.
FIG. 1 is a view showing a basic structure of a conventional image projecting apparatus using a color wheel.
Referring to FIG. 1, the conventional image projecting apparatus using a color wheel includes a light source 110, a color wheel 120, a DMD panel 130 and a projecting lens 140. In FIG. 1, the optical path of the white light is represented by one-dotted line.
The light source 110 irradiates a white light by using an arc lamp, or a laser. The color wheel 120 is rotated by a rotating means (not shown) in the arrowed direction. The color wheel 120 is divided into red (R), green (G) and blue (B) regions.
The white light, being emitted from the light source 110, is divided into red (R), green (G), and blue (B) beams through the R, G and B regions of the color wheel 120. The DMD panel 130 is provided with a plurality of micromirrors 130a. R, G and B beams are projected onto the DMD panel 130 and reflected from the micromirror 130a. The reflected R, G and B beams are transmitted through the projecting lens 140, and subsequently realize an image on the screen.
In the conventional image projecting apparatus 100 constructed as above, while the R beam passes through the R region of the color wheel 120 it can be evenly projected over the entire panel, with G and B beams blocked by the color filter. The same phenomenon also applies to G and B beams. That is, the luminosity used in the DMD panel 130 at any given time is only a third of the white light emitted from the light source 110, and thus, the brightness of the image also deteriorates.
In other words, reduction in luminosity at the DMD panel 130 causes degradation in light efficiency, and subsequently hinders maximization of the brightness of the image. Furthermore, xe2x80x98overlapping phenomenonxe2x80x99 occurs in which the respective beams on the panel partially overlap with each other at the respective adjoining areas.
Accordingly, it is an aspect of the present intention to provide an image projecting apparatus capable of improving light efficiency at a single panel, and removing partial overlapping of the respective beams at adjoining areas.
In order to achieve the above aspect and/or other features of the present invention, there is provided an image projecting apparatus, including a light source for irradiating a plurality of monochromatic lights of different wavelengths, a first light transmitting unit comprising a plurality of optical fibers through which the respective monochromatic lights pass, a first optical switch unit comprising a plurality of optical switches in a square matrix arrangement for selectively reflecting the monochromatic lights, a second optical switch unit comprising a plurality of optical switches in single file for reflecting and/or transmitting the monochromatic lights reflected from the first optical switch unit, the plurality of optical switches in odd-numbered rows being a first group while the optical switches in even-numbered rows being a second group, a square beam generator for transforming the monochromatic lights reflected from the second optical switch unit into a square beam of a predetermined aspect ratio, a panel unit for receiving the square beam of the monochromatic lights and realizing the received square beam in the form of a monochromatic color stripe of a predetermined size, and a projecting lens unit formed opposite to the panel unit, wherein either the first or the second group of the second optical switch unit periodically reflects the monochromatic lights.
According to the present invention, by using the optical switches in 3xc3x973 matrix arrangement and optical switches in single file arrangement, light utilization can be improved, and partial overlapping of the monochromatic color stripes on the panel is prevented.